This application is based on Application No. 2002-1265, filed in Japan on Jan. 8, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an electric power steering apparatus for assisting the steering force of a steering wheel of a vehicle.
2. Description of the Prior Art
FIG. 18 is a cross sectional view of a conventional electric power steering apparatus as disclosed in Japanese Patent Application Laid-Open No. 8-258730.
In this electric power steering apparatus, a motor 100 and a control circuit unit 103 for controlling a current flowing through the motor 100 are housed in a bottomed cylindrical casing 101.
The motor 100 includes a shaft 104 connected with a steering mechanism of a vehicle, a rotor 108 fixedly secured to the shaft 104, a magnet 107 arranged to surround the rotor 108, an electromagnetic clutch 105 for controlling torque transmitted to the steering mechanism in an on and off manner, and an angle sensor 106 for detecting the steering angle of a steering wheel or the rotational angle or position of the shaft 104 to generate a corresponding output to the control circuit unit 103.
In the electric power steering apparatus as constructed above, the shaft 104 is driven to rotate by means of the motor 100, so that the rotational force of the motor 104 is transmitted to the steering mechanism through the shaft 104 so as to provide torque assistance of the steering mechanism.
With the above-mentioned conventional electric power steering apparatus in which the motor 100 and the control circuit unit 103 are housed in the casing 101, there are the following problems.
(1) The motor 100 and the control circuit unit 103 can not be easily separated from each other, and hence when either one of the motor 100 and the control circuit unit 103 fails, it is necessary to replace the electric power steering apparatus on the whole.
(2) Assemblability is poor since it is necessary to assemble the motor 100 and the control circuit unit 103, which are mutually connected with each other through wiring or lead wires, into the bottomed cylindrical casing 101 at the same time.
The present invention is intended to solve the problems as referred to above, and has for its object to provide an electric power steering apparatus in which upon failure of either one of a motor and a control circuit unit, the failed one alone has to be replaced with a new one, and which is improved in assemblability.
Bearing the above object in mind, an electric power steering apparatus according to the present invention includes: a motor having a housing and a shaft disposed on an axis of the housing and connected with a steering mechanism of a vehicle, the motor being operable to assist a steering force of a steering wheel through the shaft; and a control circuit unit with a power device for driving the motor being disposed in a casing. The housing is formed with a housing opening through which lead wires pass. The casing is also formed with a casing opening through which the lead wires pass. The motor and the control circuit unit are integrated with each other with the housing opening and the casing opening disposed to correspond to each other. With the above arrangement, when either one of the motor and the control circuit unit fails, it is only necessary to replace the failed one alone, thus making it possible to reduce the cost of replacement. In addition, it only has to first assemble the motor and the control circuit unit separately from each other and then integrate the motor and the control circuit unit into a single unit in the final process, thus improving the assemblability thereof.
The above and other objects, features and advantages of the present invention will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.